Each year, many children lose their lives due to suffocation. One study shows that 54% of fatalities to children under the age of fourteen are caused by suffocation. When a child suffers from suffocation, it is likely to result in a fatal injury more than eighteen times than a non-fatal injury. Injuries from suffocation are largely categorized into two types: mechanical resistance to a passage of air and asphyxia. Both flexible and rigid materials can provide mechanical resistance to an air passage of a child. Mechanical resistance is often created when the oropharynx and/or the nasopharynx of a child is blocked externally by an object. For example, children have been suffocated by plastic bags, inflatable toys, and stacking cups. Asphyxia is suffocation caused by physiological responses to a lack of oxygen and an excess level of carbon dioxide in the body. Asphyxia occurs as a consequence of suffocation.
FIG. 1 of the accompanying drawings illustrates an inhalation mechanism 1 of a human 2. During inhalation, the diaphragm in the human body is forcefully lowered (in the direction indicated by the arrow 3) creating a negative pressure in the lungs. At the same time, air enters through the mouth 4 and/or nose 5 to the lungs. The air encounters flow resistance in the oropharynx 6 or the nasopharynx 7.
FIG. 2 illustrates an exhalation mechanism 8. During exhalation, the diaphragm is relaxed upwards (in the direction indicated by the arrow 9), creating a positive pressure in the lungs. Simultaneously, air in the lungs exits through the mouth 4 and/or nose 5. The existing air encounters flow resistance in the oropharynx 6 or the nasopharynx 7.
FIG. 3 illustrates a graph of a respiratory cycle of a human. The horizontal and vertical axes of the graph indicate time and volume, respectively. A respiratory cycle consists of inhalation and exhalation followed by a pause. A respiratory frequency ƒ can be determined from the respiratory cycle. The inhalation takes place during inspiratory time T1, and is represented by a ramp function. The exhalation takes place during expiratory time T2 and is represented by a sine decay function. A tidal volume VT indicates a volume of air inhaled and exhaled by a human. A respiration pattern consists of one or more of respiratory cycles. Total time Ttot for a respiratory cycle includes the inspiratory time, expiratory time, and pause.
In the past, some testing has been conducted on products and apparel to assess risk of suffocation by children. To accurately assess the suffocation risk, a breathing or respiration pattern of a child must be accurately simulated. However, it is difficult to accurately simulate a respiration pattern of a child since the pattern depends on many factors, such as activities, age, and gender of the child. For example, infants usually breathe through their nasal passages. During the crying, however, the nasal passage of an infant is often blocked and the infant may breathe through the oral cavities. Also, a one-year-old infant may be capable of producing a respiratory pressure (intrathoracic pressure) of up to 30 cm H2O for a brief period of time. On the other hand, a young child may be able to produce a respiratory pressure of 15 cm H2O for an extended period of time.
Also, a respiration pattern under different levels of occlusion must be accurately simulated. When a blockage causes complete occlusion to a child and the blockage is not removed, the child will likely to die after two or three minutes. When a blockage causes partial occlusion to a child, the child may survive for a longer period of time depending on the level of the occlusion, strength, endurance, age, and sleep state of the child. In addition, protective mechanisms of a child against suffocation differ based on many factors.
Consequently, a need exists for an apparatus and method capable of accurately simulating and monitoring a respiration pattern of a human, especially an infant and a young child, and offering a flexibility to simulate various respiration patterns.